Topic: Side cover repair with Gorilla Glue epoxy...are they polyethylene?

[thanantos]

I have a busted up side cover I'm trying to cobble together for now so I picked up some Gorilla Glue epoxy that would seem to be perfect. However, it says not to use it on polyethylene or polypropylene plastics.

Any idea what CB500 side covers are made of?

[Artf0rm]

It's been a long time but I think I remember Polyethylene being the most common compound in plastics in general.  It's most likely in your side covers in some form.  With that said I would test it on a safe spot before proceeding.  Some epoxies can interact with the polyethylene and make a sticky gooey paste that hardens and from which there is no return.  On the other hand you could put it on there and nothing unusual happen at all.  Just depends on the poly form in your plastic and the epoxy compound..

[MCRider]

The problem is not so much what they are made of, but what is left of it. After 30+ years the material has outgassed all the chemicals that made it soft and pliable. What's left is just a shell of its original makeup.

My CB750k2 covers broke twice. the first was a common crack that occurs near the top front of the left cover. I had it plastic welded by a guy in Chicago who has since retired.  Later, a few years ago, while removing the same cover, it cracked a large piece off the corner. I had it plastic welded by a guy in CT. real nice job.

I think any do it yourself approach is going to be frustrating. The "plastic weld" approach seems to me the best route. I do think there are some plastic wld kits availabel but for the price i didn't want to bother.

I have since decided to mothball my original covers and use some Frankenstuff replacements. They are soft and gummy and likely to hold up for my lifetime. If i went and put a high dollar paintjob on the origianl covers they would just break again, looking at them!

http://www.ctbikersguide.com/expertplasticwelding.htm

Google plastic welding motorcycle repair and you'll get educated and find resources.

Frankenstuff replacements

Weld repair from CT

[MCRider]

PS: If you call Owen at the link provided he'll tell you what its made of and what it takes to repair it. Real nice guy.

[KingCustomCycles.com]

JB Weld works great with proper surface cleaning and intelligent support for the replacement piece.  The biggest cause of breakage is old, hard, retaining grommets without lube.  I use Dow Corning DC4 on the grommets and the posts and if the grommets are stiff, replace them.  I have not broken a side cover with this regime in 7 years.  I repair them all the time though.

[cookindaddy]

+1 for King's suggestions
If you do try the glue approach, some backing material on the inside of the crack helps a lot. The epoxy I used adheres well to aluminum so I cut narrow (about 1/4 - 1/2") strips of aluminum, fine sanded the side that was going against the side cover inside and then bent the strips to conform to the profile of the side cover. Covered lightly with the glue and pressed into place. Resist the temptation to test the joint until the glue has fully cured.

[fmctm1sw]

Somewhere there is a post about using melted pvc pipe as a repair agent...

[TwoTired]

The original covers are made of molded PVC.  Polyvinyl Chloride.  Polyethylene/polypropylene feels waxy, like what milk jugs are often made of, and its that waxy feel that prevents an epoxy bond.

Epoxy binds best to coarse surfaces, so you are better off scrubbing/scratching a smooth surface before epoxying.
Also, I recommend nylon or fiberglass tape inside to bridge the crack or break to reinforce the crack.

PVC is a thermoplastic, meaning it can be shaped when heated.  This works well when the plastic is young.  As mentioned earlier, the "plasticizers" leech out of the plastic with time causing microscopic voids, as well as embrittlement.  PVC can be welded, but old PVC collapses/shrinks when heated to melting because of the microscopic voids.  This leaves a "valley" in the surface right next to and following the recent weld.  The valley can be filled with bondo or the like.

In the late 70's, I repaired a side cover crack with epoxy and nylon tape reinforcement.  It is still intact today.  I think I have pictures somewhere, if needed.

Cheers,

[spot45]

I actually did that recently and it does work.  The epoxy seeps into the fibers of the nylon tape, but make sure everything is lined up right because there is no point of no return, if you make any mistakes.  The other thing you could try is fiberglass cloth and epoxy.  I have done that with good results on side covers for some of the DOHC bikes.

[thanantos]

Thanks guys, I'll post the results!

[sopo400f]

West System makes a product called G-flex Epoxy, they do specify that it works on PCCillin and other hard to adhere surfaces. You could even lay some glass in with it.

[BeSeeingYou]

I used ABS/PVC glue for plumbing fittings.  Then beefed up the backside with epoxy and fiberglass cloth.  Epoxy will stick to PVC.

[mrbreeze]

I just started reading this post after starting on a pair covers I was going to sell. I'm not really in any hurry to do these......just something to fiddle with in between other projects. I have had these covers in my parts stash for a few years and each one em has a crack from people yanking them off of rock hard grommets like was mentioned earlier. These 2 aren't real bad so I thought I'd give it a go to fix and use them. I've had the Maier aftermarket covers on it since I got the bike in 2000 so I think I want to get me some fresh grommets and try these out after I get them sanded out & painted.
What I have done so far is put Gorilla glue inside of the crack, let it dry overnight and sand the bead down on the outside of cover. I also had drilled a hole at the end of the crack previously to starting. I'm not done sanding the outside yet but I layed down some JB weld on the inside and to fill hole I drilled. I'll go do some more to it tomorrow. Like I said.....I'm not in a rush. Just like Jed Clampett whittling a piece of wood.!!! I don't think these cracks are bad enough to warrant putting fiberglass over but you never know. If it don't work out...I'll buy from Franken Dude. I haven't heard of any problems with those.

[mrbreeze]

Here's more......

[Stev-o]

I've had pretty good luck with JB Weld

[Mr. Mike]

As Steve said. JB Weld has held up well on my broken (not cracked) side cover.